I've looked at DOA4 screenshots a bit. Nothing in depth. The thumbnails are simple enough to extract as they are very small .png's.
See Here:
The full screenshot however is an odd form of .mdi file. If you do a google search you can compare the header to your average .mdi and notice the similarities. "PTC+MSHM" According to my pal, pedrospad who has taken a more in depth look at the format; they are your average .mdi with an odd/new compression technique not usually used. Below is a link to an extracted photo. (Although not viewable!)
http://360gamesaves.com/uploads/photodata.ptc
http://grap3.heypoorplayer.org/doa4/snapshot50.ptc
http://grap3.heypoorplayer.org/doa4/snapshot50.ptc.png
http://grap3.heypoorplayer.org/doa4/snapshot70.ptc
http://grap3.heypoorplayer.org/doa4/snapshot70.ptc.png
http://en.wikipedia.org/wiki/Microsoft_ ... ing_Format